That roller coaster pictured above is the last year of the housing market in the Baltimore metro area, at a glance.

In blue -- the figure with the huge swoops and swoons -- is the year-over-year change in the number of homes sold, according to Metropolitan Regional Information Systems' stats arm. In red is the year-over-year change in the average home sale price.

The federal first-time homebuyer tax credit is what drove the number of home sales up, and then down, last year. Buyers rushed to beat the deadline (contract signed by April, closing by June -- later pushed back to September). And at least some of them were people who would otherwise have bought later in the year.

Sales began to rise again in December, but new numbers for March show we're back in declining territory year-over-year. Probably not a tremendous shock, since we're now (and for the next few months will be) comparing against the height of the 2010 tax-credit boost. The April 2010 bump was particularly large, nearly 40 percent.

Even when the tax credit was in effect, however, market activity wasn't back to normal for the region. About 1,960 homes changed hands in the metro area in March 2010. That's 100 more than this March and 330 more than March 2009, but it's less than all the previous Marches in the last decade.

In March 2000, when fewer people lived in the area, more than 2,370 homes changed hands.

Here's the news story about March home sales, complete with an anecdote about a Baltimore County home seller who found people were more interested in his house when he offered to throw in a '93 Taurus (with low mileage) as a freebie.